Embodiments of the present specification relate generally to Electrical Impedance Tomography, and more particularly to systems and methods for simultaneous image reconstruction and estimation of time-varying electrode contact impedances in Electrical Impedance Tomography.
Electrical Impedance Tomography (EIT) is a non-invasive imaging tool with applications in numerous fields such as medicine, geophysics, environmental sciences, and nondestructive testing of materials. In recent years, EIT has being increasingly used in medical applications such as detection of pulmonary emboli, monitoring of apnea, monitoring of heart function and blood flow, and breast cancer detection. Also, some examples of non-medical applications of EIT include locating underground mineral deposits, detection of leaks in underground storage tanks, detection of corrosion and small defects such as cracks or voids in metals.
Typically, use of the EIT technique for imaging entails positioning a plurality of electrodes on the skin around an anatomical region in a subject being examined. Further, a low voltage alternating electrical current is applied to one or more electrodes. A resulting potential difference is measured between each pair of electrodes among the plurality of electrodes. An image of impedance within the body is generated based on the measured potential differences. Techniques such as parallel data collection and noise reduction have enabled EIT systems to provide clinically useful images of dynamic phenomena.
One significant problem with EIT is that the quality of each electrode's contact with the body varies significantly over time. Specifically, occurrence of electrochemical processes results in significant variations in the impedance of the skin-electrode boundary over time. Additionally, any motion by the subject being imaged may also result in variations in the impedance of the skin-electrode boundary over time. Some currently available EIT techniques attempt to maximize sensitivity to changes in conductivity and permittivity within the anatomical region by applying currents to all the electrodes. Certain other techniques entail use of compound electrodes. However, use of the compound electrodes calls for non-standard electrode designs and system configurations, thereby resulting in increased cost of the EIT system.